So while there isn't a mandatory standard, 80 plus does have certain test requirements to pass certification;
https://www.clearesult.com/80plus/program-details
For example this is the power supply I have:
https://www.clearesult.com/80plus/sites/80plus/files/manufacturer-certificate/thermaltake-spr700ah2nk2-smart-rgb-700w-4573.pdf
At 700W output power, input power is 845.50W, that is a 16.83% loss to heat. 145W is quite a bit, but I don't run my power supply at 100%. 24/7 usage is 3.48KWh lost due to inefficiency and where I live costs 72 cents(My power is $0.2079/kwh) per day, over a year that is $264.
If I got a 80 plus bronze such as:
https://www.clearesult.com/80plus/sites/80plus/files/manufacturer-certificate/be-quiet-s9cm700w-2103.pdf
Then at 700W loading, I'd be drawing 814.80W, a saving of 30.7W. Saving me 15 cents per day or $55 per year of savings.
Using this specification chart: (For 700W output ie 100% load(for me anyway))

80 plus: 853.6W input for 700W output, 76 cents per day, $279 per year
80 plus bronze: 823.5W input, 61 cents per day, $224 per year
80 plus silver: 804.5W input, 52 cents per day, $190 per year
80 plus gold: 786.5W input, 43 cents per day, $157 per year
80 plus platinum: 777.7W input, 38 cents per day, $141 per year
80 plus titanium: 769.2W input, 34 cents per day, $126 per year
Numbers are for how much power costs me
